Method of forming interlayer insulating film

ABSTRACT

A material containing, as a main component, an organic silicon compound represented by the following general formula: 
     
         R.sup.1.sub.x Si(OR.sup.2).sub.4-x 
    
     (where R 1  is a phenyl group or a vinyl group; R 2  is an alkyl group; and x is an integer of 1 to 3) is caused to undergo plasma polymerization or react with an oxidizing agent to form an interlayer insulating film composed of a silicon oxide film containing an organic component. As the organic silicon compound where R 1  is a phenyl group, there can be listed phenyltrimethoxysilane or diphenyldimethoxysilane. As the organic silicon compound where R 1  is a vinyl group, there can be listed vinyltrimethoxysilane or divinyldimethoxysilane.

BACKGROUND OF THE INVENTION

The present invention relates to a method of forming an interlayerinsulating film in a semiconductor device.

Known interlayer insulating films formed in semiconductor devicesinclude a silicon oxide film, a silicon oxide film composed of anorganic SOG (Spin-On-Glass) containing an organic component, and anorganic polymer film.

In general, an interlayer insulating film formed in a semiconductordevice is required to have a sufficiently low dielectric constant toachieve lower wiring capacitance and sufficiently high heat resistanceto withstand a semiconductor manufacturing process.

With the increasing miniaturization of an LSI formed on a semiconductorsubstrate, wiring capacitance which is parasitic capacitance betweenmetal wires has remarkably increased, while degraded performance of theLSI due to a wiring delay caused thereby has presented a seriousproblem. The wiring capacitance is determined by the size of a spacebetween the metal wires and by the magnitude of the dielectric constantof an interlayer insulating film present in the space. To reduce thewiring capacitance, therefore, it is important to reduce the dielectricconstant of the interlayer insulating film.

If an interlayer insulating film with low heat resistance is used, athermal treatment at about 400° C. performed in a semiconductormanufacturing process will soften the interlayer insulating film andundulate wiring, which may cause a fatal failure such as a disconnectionor short circuit. This is why the interlayer insulating film is requiredto have sufficiently high heat resistance to withstand the thermaltreatment at about 400° C.

Since an interlayer insulating film composed of a silicon oxide film hasan undesirably high dielectric constant, there has been proposed afluorine-doped silicon oxide film made of silicon oxide doped withfluorine. Although the dielectric constant of the fluorine-doped siliconoxide film has been lowered by bonding a fluorine atom having lowpolarizability to a silicon atom composing the oxide film, the moistureabsorbing property thereof increases with an increase in the amount offluorine added thereto, so that a minimum dielectric constant attainableis about 3.5. Hence, it is difficult to use silicon oxide filmsincluding the fluorine-doped silicon oxide film as interlayer insulatingfilms in an extremely miniaturized LSI.

In place of silicon oxide films, the use of an organic SOG film ororganic polymer film as an interlayer insulating film in an extremelyminiaturized LSI is under consideration because of its low dielectricconstant.

The organic SOG film is formed by thermally curing a solution containingsilica or siloxane each having an organic component such as a methylgroup or a phenyl group. Since the organic component remains in the filmeven after thermal curing, a low dielectric constant of about 3.0 isattained.

As a first conventional embodiment, a method of forming an interlayerinsulating film composed of an organic SOG film will be described withreference to FIGS. 6(a) to 6(d).

First, as shown in FIG. 6(a), first-level metal wires 2 are formed on asemiconductor substrate 1, followed by a first silicon oxide film 3formed over the entire surface of the semiconductor substrate 1including the first-level metal wires 2 by plasma CVD using a gasmixture of, e.g., tetraethoxysilane and oxygen as a raw material.Thereafter, an organic SOG agent is applied onto the first silicon oxidefilm 3 by spin coating and thermally cured to form an organic SOG film4.

Then, as shown in FIG. 6(b), the entire surface of the organic SOG film4 is etched back such that the portions thereof overlying thefirst-level metal wires 2 are removed.

Next, as shown in FIG. 6(c), a second silicon oxide film 5 is formedover the entire surface of the silicon oxide film 3 including theremaining organic SOG film 4 by, e.g., plasma CVD using a gas mixtureof, e.g., tetraethoxysilane and oxygen as a raw material.

Next, as shown in FIG. 6(d), contact holes are formed in the first andsecond silicon oxide films 3 and 5 by using a resist pattern as a mask,which is then removed by using an oxygen plasma. Subsequently, a metalmaterial is filled in the contact holes to form contacts. After that,second-level metal wires 7 are formed on the second silicon oxide film5, resulting in a structure having an interlayer insulating filmconsisting of the first silicon oxide film 3, the organic SOG film 4,and the second silicon oxide film 5 between the first- and second-levelmetal wires 2 and 7.

As a second conventional embodiment, a method of forming an interlayerinsulating film composed of a fluorinated amorphous carbon film, whichis an organic polymer film, will be described. As disclosed in atechnical report (Extended Abstracts of the 1995 InternationalConference on Solid State Devices and Materials, Osaka, 1995,pp.177-179), a fluorinated amorphous carbon film is formed by plasma CVDusing, as a raw material, a mixture of a hydrocarbon-based componentsuch as CH₄ and a fluorine-containing component such as CF₄.

After the gas mixture is introduced into a reaction chamber of aparallel-plate plasma CVD apparatus, the pressure inside the reactionchamber is held at several hundreds of Torr. When RF power on the orderof 100 to 300 W at 13.56 MHz is applied to parallel-plate electrodes inthe reaction chamber, the gas mixture is partially decomposed togenerate monomers, ions, and radicals, which undergo plasmapolymerization, resulting in a fluorinated amorphous carbon film as aplasma polymerization film deposited on a semiconductor substrate. Thefluorinated amorphous carbon film thus formed has a low dielectricconstant of 2.0 to 2.5 immediately after deposition.

However, since the foregoing organic SOG film is formed by repeatedlyperforming the steps of applying the organic SOG agent and thermallycuring the applied organic SOG agent several times, it has thedisadvantages of poor film formability resulting from a large amount oftime required by the formation of the organic SOG film and high costresulting from the major portion of the agent wasted during the spincoating.

In the case where the etch-back process, as illustrated in FIG. 6(b), isnot performed with respect to the entire surface of the organic film 4before contact holes are formed in the organic SOG film 4 and in thefirst silicon oxide film 3 by using the resist pattern as a mask, whichis then removed by using an oxygen plasma, and contacts are formed byfilling the metal material in the contact holes, the following problemsarise. In the step of removing the resist pattern by using the oxygenplasma, SiCH₃ contained in the organic SOG films 4 exposed at thesidewalls of the contact holes reacts with the oxygen plasma to generateSiOH, which is condensed by dehydration to generate H₂ O in the step offilling the metal material in the contact holes. The resulting H₂ Ocauses the oxidization and contamination of the metal forming thecontacts, leading to faulty conduction at a contact.

As for the organic polymer film composed of the fluorinated amorphouscarbon film, it has the advantage of an extremely low dielectricconstant over the organic SOG film but is inferior thereto in heatresistance because of its low glass transition temperature. When theconventional fluorinated amorphous carbon film is subjected to a thermaltreatment at a temperature of 300° C. or more, the thickness of the filmis significantly reduced, while the dielectric constant thereof isgreatly increased. For example, if a fluorinated amorphous carbon filmmade from CH₄ and CF₄ and having a dielectric constant of 2.2immediately after deposition is subjected to a thermal treatment at atemperature of 300° C. for 1 hour, the film contracts till the thicknessthereof is reduced to about 65% of the original thickness immediatelyafter deposition, which is a 35% reduction, while the dielectricconstant thereof is increased to about 2.8.

It is to be noted that the foregoing problems are not limited to theinterlayer insulating film formed between upper and lower metallizationlayers but also arise in an interlayer insulating film between metalwires included in a single metallization layer.

SUMMARY OF THE INVENTION

In view of the foregoing, a first object of the present invention is toimprove the film formability, cost efficiency, and processability of aninterlayer insulating film composed of an organic SOG film. A secondobject of the present invention is to improve the heat resistance of aninterlayer insulating film composed of an organic polymer film.

To attain the first object, there is provided a first method of formingan interlayer insulating film of the present invention, wherein amaterial containing, as a main component, an organic silicon compoundrepresented by the following general formula:

    R.sup.1.sub.x Si(OR.sup.2).sub.4-x

(where R¹ is a phenyl group or a vinyl group; R² is an alkyl group; andx is an integer of 1 to 3) is caused to undergo plasma polymerization orreact with an oxidizing agent to form an interlayer insulating filmcomposed of a silicon oxide film containing an organic component.

In accordance with the first method of forming an interlayer insulatingfilm, since the resulting interlayer insulating film contains, as a maincomponent, the organic silicon compound represented by the followinggeneral formula:

    R.sup.1.sub.x Si(OR.sup.2).sub.4-x

(where R¹ is a phenyl group or a vinyl group; R² is an alkyl group; andx is an integer of 1 to 3) or by the following general formula:

    R.sup.1.sub.x SiH.sub.4-x

(where R¹ is a phenyl group or a vinyl group; and x is an integer of 1to 3), the proportion of SiCH₃ contained in the interlayer insulatingfilm is much lower than contained in a conventional organic SOG film,though the dielectric constant thereof is equal to that of theconventional organic SOG film. Accordingly, even when the interlayerinsulating film is exposed to an oxygen plasma, only a small amount ofSiOH is generated and the dehydration condensation of SiOH does notoccur in the step of filling a metal material in contact holes. As aresult, H₂ O is not generated and hence the problem of faulty conductionat a contact does not occur.

Moreover, since the silicon oxide film containing the organic componentis formed by causing the material containing the organic siliconcompound as the main component to undergo plasma polymerization or reactwith an oxidizing agent in accordance with the first method of formingan interlayer insulating film, it is no more necessary to perform thesteps of applying an organic SOG agent and curing the applied organicSOG agent, resulting in excellent film formability.

In the first method of forming an interlayer insulating film, theorganic silicon compound represented by the general formula: R¹ _(x)Si(OR²)_(4-x) is preferably phenyltrimethoxysilane ordiphenyldimethoxysilane and the organic silicon compound represented bythe general formula: R¹ _(x) SiH_(4-x) is preferably phenylsilane ordiphenylsilane.

In the first method of forming an interlayer insulating film, theorganic silicon compound represented by the general formula: R¹ _(x)Si(OR²)_(4-x) is preferably vinyltrimethoxysilane ordivinyldimethoxysilane and the organic silicon compound represented bythe general formula: R¹ _(x) SiH_(4-x) is preferably vinylsilane ordivinylsilane.

To attain the second object, there is provided a second method offorming an interlayer insulating film according to the presentinvention, wherein a material containing, as a main component, afluorinated carbon compound having two or more double bonds of carbonatoms in a molecule thereof is caused to undergo plasma polymerizationto form an interlayer insulating film composed of a fluorinatedamorphous carbon film.

In accordance with the second method of forming an interlayer insulatingfilm, since the fluorinated carbon compound has two or more double bondsof carbon atoms in a molecule thereof, radicals each having three ormore unoccupied bonds are likely to be generated when the fluorinatedcarbon compound is decomposed by a plasma. These radicals promotethree-dimensional polymerization and ensure three-dimensional bonding inpolymer composing the plasma polymerization film, which positivelyincreases the crosslinking density and glass transition temperature ofthe resulting interlayer insulating film, so that the heat resistancethereof is remarkably improved.

In the second method of forming an interlayer insulating film, thefluorinated carbon compound is preferably composed only of carbon atomsand fluorine atoms. This prevents the plasma polymerization film fromcontaining hydrogen, so that the dielectric constant of the resultinginterlayer insulating film is lowered.

In this case, the fluorinated carbon compound is more preferablyhexafluoro-1,3-butadiene.

To attain the second object, there is provided a third method of formingan interlayer insulating film according to the present invention,wherein a material containing, as a main component, a fluorinated carboncompound having a triple bond of carbon atoms in a molecule thereof iscaused to undergo plasma polymerization to form an interlayer insulatingfilm composed of a fluorinated amorphous carbon film.

In accordance with the third method of forming an interlayer insulatingfilm, since the fluorinated carbon compound has a triple bond of carbonatoms in a molecule thereof, radicals each having three or moreunoccupied bonds are likely to be generated when the fluorinated carboncompound is decomposed by a plasma. These radicals promotethree-dimensional polymerization and ensure three-dimensional bonding inpolymer composing the plasma polymerization film, which positivelyincreases the crosslinking density and glass transition temperature ofthe resulting interlayer insulating film, so that the heat resistancethereof is remarkably improved.

In the third method of forming an interlayer insulating film, thefluorinated carbon compound is preferably composed only of carbon atomsand fluorine atoms. This prevents the plasma polymerization film fromcontaining hydrogen, so that the dielectric constant of the resultinginterlayer insulating film is lowered.

In this case, the fluorinated carbon compound is more preferablyhexafluoro-2-butyne.

To attain the second object, there is provided a fourth method offorming an interlayer insulating film according to the presentinvention, wherein a material containing, as a main component, afluorinated carbon compound having a polycyclic structure in a moleculethereof is caused to undergo plasma polymerization to form an interlayerinsulating film composed of a fluorinated amorphous carbon film.

In accordance with the fourth method of forming an interlayer insulatingfilm, since the fluorinated carbon compound has a polycyclic structurein a molecule thereof, radicals each having three or more unoccupiedbonds are likely to be generated when the fluorinated carbon compound isdecomposed by a plasma. These radicals promote three-dimensionalpolymerization and ensure three-dimensional bonding in polymer composingthe plasma polymerization film, which positively increases thecrosslinking density and glass transition temperature of the resultinginterlayer insulating film, so that the heat resistance thereof isremarkably improved.

In the fourth method of forming an interlayer insulating film, thefluorinated carbon compound is preferably composed only of carbon atomsand fluorine atoms. This prevents the plasma polymerization film fromcontaining hydrogen, so that the dielectric constant of the resultinginterlayer insulating film is lowered.

In the fourth method of forming an interlayer insulating film, thefluorinated carbon compound preferably has a condensed cyclic structurein the molecule thereof. This increases the likelihood that radicalseach having three or more unoccupied bonds are generated, so that thecrosslinking density of the resulting interlayer insulating film isfurther increased, resulting in higher heat resistance thereof.

In this case, the fluorinated carbon compound is more preferablyperfluorodecalin, perfluorofluorene, orperfluoro(tetradecahydrophenanthrene).

In a fifth method of forming an interlayer insulating film according tothe present invention, a material containing, as a main component, a gasmixture of an organic silicon compound composed of a compoundrepresented by the following general formula:

    R.sup.1.sub.x Si(OR.sup.2).sub.4-x

(where R¹ is a phenyl group or a vinyl group; R² is an alkyl group; andx is an integer of 1 to 3) or of a siloxane derivative and a fluorinatedcarbon compound is caused to undergo plasma polymerization or react withan oxidizing agent to form an interlayer insulating film composed of asilicon oxide film containing a fluorinated carbon.

In accordance with the fifth method of forming an interlayer insulatingfilm, the silicon oxide film containing a fluorinated carbon is formedby causing the material containing, as the main components, the organicsilicon compound and the fluorinated carbon compound to undergo plasmapolymerization or react with the oxidizing agent so that the resultinginterlayer insulating film contains the organic silicon compound and thefluorinated carbon compound, which significantly lowers the dielectricconstant of the interlayer insulating film. Moreover, since the steps ofapplying the organic SOG agent and curing the applied organic SOG agent,which have been necessary to form the conventional organic SOG film, areno more necessary, similarly to the first method of forming aninterlayer insulating film, excellent film formability is achieved.

In a sixth method of forming an interlayer insulating film according tothe present invention, a material containing, as a main component, a gasmixture of an organic silicon compound and a fluorinated carbon compoundhaving two or more double bonds of carbon atoms in a molecule thereof iscaused to undergo plasma polymerization or react with an oxidizing agentto form an interlayer insulating film composed of a silicon oxide filmcontaining a fluorinated carbon.

In accordance with the sixth method of forming an interlayer insulatingfilm, the silicon oxide film containing a fluorinated carbon is formedby causing the material containing, as the main component, the gasmixture of the organic silicon compound and the fluorinated carboncompound to undergo plasma polymerization or react with the oxidizingagent, so that the resulting interlayer insulating film contains theorganic silicon compound and the fluorinated carbon compound, whichsignificantly lowers the dielectric constant of the interlayerinsulating film. Moreover, since the fluorinated carbon compound has twoor more double bonds of carbon atoms in a molecule thereof, similarly tothe second method of forming an interlayer insulating film, radicalseach having three or more unoccupied bonds are likely to be generatedwhen the fluorinated carbon compound is decomposed by a plasma. Theseradicals promote three-dimensional polymerization and allow theformation of a silicon oxide film containing a fluorinated carbon with ahigh crosslinking density and excellent heat resistance.

In a seventh method of forming an interlayer insulating film accordingto the present invention, a material containing, as a main component, agas mixture of an organic silicon compound and a fluorinated carboncompound having a triple bond of carbon atoms in a molecule thereof iscaused to undergo plasma polymerization or react with an oxidizing agentto form an interlayer insulating film composed of a silicon oxide filmcontaining a fluorinated carbon.

In accordance with the seventh method of forming an interlayerinsulating film, the silicon oxide film containing a fluorinated carbonis formed by causing the material containing, as the main component, thegas mixture of the organic silicon compound and the fluorinated carboncompound to undergo plasma polymerization or react with the oxidizingagent, so that the resulting interlayer insulating film contains theorganic silicon compound and the fluorinated carbon compound, whichsignificantly lowers the dielectric constant of the interlayerinsulating film. Moreover, since the fluorinated carbon compound has atriple bond of carbon atoms in a molecule thereof, similarly to thethird method of forming an interlayer insulating film, radicals eachhaving three or more unoccupied bonds are likely to be generated whenthe fluorinated carbon compound is decomposed by a plasma. Theseradicals promote three-dimensional polymerization and allow theformation of a silicon oxide film containing a fluorinated carbon with ahigh crosslinking density and excellent heat resistance.

In an eighth method of forming an interlayer insulating film accordingto the present invention, a material containing, as a main component, agas mixture of an organic silicon compound and a fluorinated carboncompound having a polycyclic structure is caused to undergo plasmapolymerization or react with an oxidizing agent to form an interlayerinsulating film composed of a silicon oxide film containing afluorinated carbon.

In accordance with the eighth method of forming an interlayer insulatingfilm, the silicon oxide film containing a fluorinated carbon is formedby causing the material containing, as the main component, the gasmixture of the organic silicon compound and the fluorinated carboncompound to undergo plasma polymerization or react with the oxidizingagent, so that the resulting interlayer insulating film contains theorganic silicon compound and the fluorinated carbon compound, whichsignificantly lowers the dielectric constant of the interlayerinsulating film. Moreover, since the fluorinated carbon compound has apolycyclic structure in a molecule thereof, similarly to the fourthmethod of forming an interlayer insulating film, radicals each havingthree or more unoccupied bonds are likely to be generated when thefluorinated carbon compound is decomposed by a plasma. These radicalspromote three-dimensional polymerization and allow the formation of asilicon oxide film containing a fluorinated carbon with a highcrosslinking density and excellent heat resistance.

In the sixth to eighth methods of forming an interlayer insulating film,the organic silicon compound is composed of a compound represented bythe following general formula:

    R.sup.1.sub.x Si(OR.sup.2).sub.4-x

(where R¹ is a phenyl group or a vinyl group; R² is an alkyl group; andx is an integer of 1 to 3) or of a siloxane derivative. This improvesthe film formability, dielectric constant, and heat resistance of theresulting interlayer insulating film.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a plasma CVD apparatus for use in a methodof forming an interlayer insulating film according to each of theembodiments of the present invention;

FIGS. 2(a) to 2(d) are cross-sectional views illustrating individualprocess steps in accordance with a first method of manufacturing asemiconductor device to which the method of forming an interlayerinsulating film according to each of the embodiments of the presentinvention is applied;

FIGS. 3(a) to 3(d) are cross-sectional views illustrating individualprocess steps in accordance with a second method of manufacturing asemiconductor device to which the method of forming an interlayerinsulating film according to each of the embodiments of the presentinvention is applied;

FIG. 4 shows the result of analysis when Fourier transform infraredspectroscopy was performed with respect to an interlayer insulating filmaccording to the first embodiment and a conventional organic SOG film;

FIG. 5 shows the result of analysis when Fourier transform infraredspectroscopy was performed with respect to interlayer insulating filmsaccording to the first embodiment, which had undergone no thermaltreatment, a thermal treatment at 450° C., and a thermal treatment at500° C.; and

FIGS. 6(a) to 6(d) are cross-sectional views illustrating individualprocess steps in accordance with a conventional method of forming aninterlayer insulating film.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to FIG. 1, a description will be given first to a CVDapparatus for use in a method of forming an interlayer insulating filmaccording to each of the embodiments of the present invention, whichwill be described later.

FIG. 1 schematically shows the structure of a parallel-plate plasma CVDapparatus. As shown in the drawing, a semiconductor substrate 12 made ofsilicon and a sample stage 13, which is to serve as a lower electrode,are disposed in a hermetic reaction chamber 11. The sample stage 13 isconnected to a first RF power source 15 or to the ground via achange-over switch 14. The sample stage 13 is internally provided with aheater (not shown) for heating the semiconductor substrate 12 placed onthe sample stage 13 to a specified temperature. In a position opposingthe sample stage 13 in the reaction chamber 11, there is provided ashower head 16, which is to serve as an upper electrode. The shower head16 is connected to a second RF power source 17 for supplying RF power at13.56 MHz.

The reaction chamber 11 is provided with first, second, and third gassupply lines 21, 22, and 23 for introducing a gas into the reactionchamber 11. The first gas supply line 21 is provided with a firstcontainer 24 for containing a liquid raw material therein. When thefirst container 24 is supplied with carrier gas at a flow ratecontrolled by a mass flow controller (not shown), the bubbled gas isintroduced from the first container 24 into the reaction chamber 11. Thesecond gas supply line 22 is provided with a second container 25 forcontaining a liquid raw material therein. When the second container 25is supplied with carrier gas at a flow rate controlled by a mass flowcontroller (not shown), the bubbled gas is introduced from the secondcontainer 25 into the reaction chamber 11. Since the reaction chamber 11is connected to a vacuum pump 26, the reaction chamber 11 can beevacuated by driving the vacuum pump 26 so that the gases are exhaustedfrom the reaction chamber 11.

Below, a first method of manufacturing a semiconductor device to whichthe method of forming an interlayer insulating film according to each ofthe embodiments of the present invention is applied will be describedwith reference to FIGS. 2(a) to 2(d).

First, as shown in FIG. 2(a), first metal wires 101 made of, e.g.,aluminum are formed on a semiconductor substrate 100. Then, as shown inFIG. 2(b), an interlayer insulating film 102 is deposited over thesemiconductor substrate 100 including the first metal wires 101. As fora method of forming the interlayer insulating film 102, it will bedescribed later.

Next, as shown in FIG. 2(c), the interlayer insulating film 102 issubjected to planarization. Thereafter, as shown in FIG. 2(d), a contact103 is formed in the interlayer insulating film 102, followed by secondmetal wires 104 made of, e.g., aluminum which are formed on theinterlayer insulating film 102.

Below, a second method of manufacturing a semiconductor device to whichthe method of forming an interlayer insulating film according to each ofthe embodiments of the present invention will be described withreference to FIGS. 3(a) to 3(d).

First, as shown in FIG. 3(a), a first silicon nitride film 201, a firstinterlayer insulating film 202, a second silicon nitride film 203, and asecond interlayer insulating film 204 are sequentially deposited on asemiconductor substrate 200. As for a method of forming the first andsecond interlayer insulating films 202 and 204, it will be describedlater.

Next, as shown in FIG. 3(b), the second silicon nitride film 203 and thesecond interlayer insulating film 204 are patterned by photolithographyto form openings 205 for forming a wiring pattern. Then, the firstsilicon nitride film 201 and the first interlayer insulating film 202are patterned by photolithography to form openings for contacts. In thiscase, the second silicon nitride film 203 serves as an etching stopperagainst etching performed with respect to the second interlayerinsulating film 204, while the first silicon nitride film 201 serves asan etching stopper against etching performed with respect to the firstinterlayer insulating film 202.

Next, as shown in FIG. 3(c), a metal film 207 made of, e.g., copper isdeposited over the entire surface of the semiconductor substrate 200 bysputtering or CVD and caused to reflow by a thermal treatment to befilled in the openings 205 for forming a wiring pattern and in theopenings 206 for contacts.

The metal film 207 is then subjected to CMP to form metal wires 208 andcontacts 209 as shown in FIG. 3(d), resulting in buried wiring having adual damascene structure.

(First Embodiment)

An interlayer insulating film according to a first embodiment is aplasma polymerization film formed by inducing plasma polymerization of amaterial containing, as a main component, phenyltrimethoxysilane whichis an organic silicon compound represented by the following generalformula:

    R.sup.1.sub.x Si(OR.sup.2).sub.4-x

(where R¹ is a phenyl group or a vinyl group; R² is an alkyl group; andx is an integer of 1 to 3).

A description will be given to a method of forming the interlayerinsulating film according to the first embodiment.

First, the semiconductor substrate 12 is placed on the sample stage 13heated to, e.g., 400° C. and grounded by the change-over switch 14 andthen the reaction chamber 11 is evacuated by the vacuum pump 26.

Next, phenyltrimethoxysilane represented by the following ChemicalFormula 1: ##STR1## is contained in the first container 24, whilecarrier gas composed of, e.g., argon is supplied at a flow rate of 480cc/min to the first container 24 so that bubbled phenyltrimethoxysilaneis introduced into the reaction chamber 11.

Next, the pressure inside the reaction chamber 11 is set to about 1.0Torr and RF power of 250 W at a frequency of 13.56 MHz is applied fromthe second RF power source 17 to the shower head 16 serving as the upperelectrode. During the process, phenyltrimethoxysilane gas is partiallydecomposed to generate monomers, ions, and radicals as decompositionproducts, which are polymerized to form the interlayer insulating filmmade of the plasma polymerization film on the semiconductor substrate12. The structure of the plasma polymerization film is diagrammaticallyshown by the following Chemical Formula 2: ##STR2##

Since the interlayer insulating film according to the first embodimentis formed by plasma CVD, it is unnecessary to repeatedly perform thesteps of applying the organic SOG agent and thermally curing the appliedSOG agent several times, resulting in improved film formability andlower cost.

In addition, since the interlayer insulating film according to the firstembodiment contains SiCH₃ in an amount much smaller than in theconventional organic SOG film, a minimum amount of SiOH is generatedeven when the interlayer insulating film is etched by using an oxygenplasma. Consequently, the step of filling metal in contact holes is freefrom the phenomenon that SiOH is condensed by dehydration to generate H₂O and cause faulty conduction at a contact.

FIG. 4 shows the result of analysis when Fourier transform infraredspectroscopy (hereinafter referred to as FT-IR) was performed withrespect to the interlayer insulating film according to the firstembodiment and to the conventional organic SOG film. In contrast to thespectrum obtained from the conventional organic SOG film which exhibitsa distinct peak of absorbance in the vicinity of a wave number of 1300cm⁻¹, the spectrum obtained from the interlayer insulating filmaccording to the first embodiment exhibits only a small peak ofabsorbance in the vicinity of a wave number of 1300 cm⁻¹, whichindicates that the interlayer insulating film according to the firstembodiment contains a smaller amount of SiCH₃ than the conventionalorganic SOG film.

FIG. 5 shows the result of analysis when FT-IR was performed withrespect to interlayer insulating films which had undergone no thermaltreatment, a thermal treatment at 450° C. in a nitrogen atmosphere, anda thermal treatment at 500° C. in a nitrogen atmosphere. Since nodifference is observed between the FT-IR spectra obtained from theinterlayer insulating films with no thermal treatment and with thethermal treatments at 450° C. and 500° C., it will be understood thatthe interlayer insulating film according to the first embodiment hassufficiently high heat resistance to withstand an LSI manufacturingprocess.

The dielectric constant of the interlayer insulating film according tothe first embodiment was about 3.0. After the interlayer insulating filmwas allowed to stand at room temperature for about 2 weeks, thedielectric constant thereof was measured again to be about 3.1. Thisindicates that the interlayer insulating film according to the firstembodiment has stable film quality scarcely varying with time.

The density of leakage currents was also measured to be about 4.5×10⁻⁸A/cm² at 5 MV/cm, which was satisfactory.

Although the pressure inside the reaction chamber 11 has been set toabout 1.0 Torr, it is not limited thereto but may be set at any valuewithin the range of 100 mTorr to 20 Torr. More preferably, the pressureinside the reaction chamber 11 is within the range of 0.5 to 5.0 Torr.

Although the semiconductor substrate 12 has been heated to 400° C., itis not limited thereto but may be heated to any temperature within therange of 25 to 500° C. If the semiconductor substrate 12 is heated to atemperature over 400° C., however, aluminum composing the metal wiresformed on the semiconductor substrate 12 will lose heat resistance, sothat the semiconductor substrate 12 is preferably heated to atemperature equal to or lower than 400° C. If the temperature of thesemiconductor substrate 12 is less than 200° C., on the other hand, anundesired component may be contained in the interlayer insulating filmbeing formed, so that the semiconductor substrate 12 is preferablyheated to a temperature of 200° C. or more.

The RF power applied to the shower head 16 as the upper electrode mayhave any value within the range of 100 to 1000 W. More preferably, theRF power has a value within the range of 250 to 500 W.

As compounds represented by the foregoing general formula: R¹ _(x)Si(OR²)_(4-x) where R¹ is a phenyl group, there can be listeddiphenyldimethoxysilane (Ph₂ --Si--(OCH₃)₂) in addition tophenyltrimethoxysilane. As compounds represented by the foregoinggeneral formula: R¹ _(x) Si(OR²)_(4-x) where R¹ is a vinyl group, therecan be listed vinyltrimethoxysilane (CH₂ ═CH--Si--(OCH₃)₃) anddivinyldimethoxysilane ((CH₂ ═CH)₂ --Si--(OCH₃)₂).

Although the first embodiment has formed the interlayer insulating filmcomposed of the plasma polymerization film by causing the materialhaving, as a main component, an organic silicon compound represented bythe general formula:

    R.sup.1.sub.x Si(OR.sup.2).sub.4-x

to undergo plasma polymerization, the interlayer insulating film mayalso be formed by causing the material having, as a main component, anorganic silicon compound represented by the following general formula:

    R.sup.1.sub.x SiH.sub.4-x

(where R¹ is a phenyl group or a vinyl group; and x is an integer of 1to 3) to undergo plasma polymerization or by causing the materialhaving, as a main component, an organic silicon compound represented bythe forgoing general formula:

    R.sup.1.sub.x Si(OR.sup.2).sub.4-x

or by the foregoing general formula:

    R.sup.1.sub.x SiH.sub.4-x

to react with an oxidizing agent made of, e.g., O₂ or H₂ O. In thiscase, O₂ gas, H₂ O gas, or the like is introduced into the reactionchamber 11 through the third gas supply line 23 in the CVD apparatusshown in FIG. 1.

As compounds represented by the foregoing general formula: R¹ _(x)SiH_(4-x) where R₁ is a phenyl group, there can be listed phenylsilaneand diphenylsilane. As compounds represented by the foregoing generalformula: R¹ _(x) SiH_(4-x) where R₁ is a vinyl group, there can belisted vinylsilane or divinylsilane.

(Second Embodiment)

An interlayer insulating film according to a second embodiment is afluorinated amorphous carbon film formed by inducing plasmapolymerization of a material having, as a main component,1,1,1,3,3-pentafluorpropene which is a fluorinated carbon compoundhaving a double bond of carbon atoms in a molecule thereof andcontaining a hydrogen atom.

A description will be given to a method of forming the interlayerinsulating film according to the second embodiment.

First, the semiconductor substrate 12 is placed on the sample stage 13grounded by the change-over switch 14 and then the reaction chamber 11is evacuated by the vacuum pump 26.

Next, 1,1,1,3,3-pentafluoropropene is contained in the first container24, while carrier gas composed of, e.g., argon is supplied at a flowrate of 50 to 500 sccm to the first container 24 so that bubbled1,1,1,3,3-pentafluoropropene is introduced into the reaction chamber 11.After the pressure inside the reaction chamber 11 is set to 100 to 500mTorr, RW power of 100 to 500 W at a frequency of 13.56 MHz is appliedfrom the second RF power source 17 to the shower head 16 serving as theupper electrode. During the process, 1,1,1,3,3-pentafluoropropene gas ispartially decomposed to generate monomers, ions, and radicals asdecomposition products, which are polymerized to form the interlayerinsulating film made of the plasma polymerization film on thesemiconductor substrate 12.

Since the plasma polymerization film contains1,1,1,3,3-pentafluoropropene as a main component, the interlayerinsulating film composed thereof was a fluorinated amorphous carbon filmcontaining a carbon atom, a fluorine atom, and a hydrogen atom. Thefluorinated amorphous carbon film had a dielectric constant of 2.5immediately after deposition.

Since the plasma polymerization film is formed from ions and radicalswhich are decomposition products resulting from the decomposition of thegas in the plasma and have reacted on the semiconductor substrate 12,the properties of the decomposition products present in the plasmadeeply influence the structure of the plasma polymerization film.Moreover, the heat resistance of the plasma polymerization film isclosely related to the crosslinking density thereof, which determinesthe structure of the plasma polymerization film.

In a conventional plasma polymerization film composed of a fluorinatedamorphous carbon film, bonding in polymer composing the plasmapolymerization film is linear and one-dimensional so that the glasstransition temperature thereof is low, which may account for poor heatresistance.

In the interlayer insulating film according to the second embodiment, bycontrast, bonding in polymer composing the plasma polymerization filmtends to be three-dimensional, so that the crosslinking density andglass transition temperature thereof become high, resulting in excellentheat resistance. Specifically, since 1,1,1,3,3-pentafluoropropene has adouble bond of carbon atoms in a molecule thereof, decompositionproducts resulting from the decomposition of1,1,1,3,3-pentafluoropropene in the plasma are likely to undergo acrosslinking reaction during the formation of the plasma polymerizationfilm on the semiconductor substrate 12. Accordingly, the resultingplasma polymerization film has a high glass transition temperature andexcellent heat resistance.

To evaluate the heat resistance of the interlayer insulating filmaccording to the second embodiment, the semiconductor substrate 12formed with the fluorinated amorphous carbon film according to thesecond embodiment was held at a temperature of 400° C. in vacuum for 1hour. The thickness and dielectric constant of the fluorinated amorphouscarbon film were then measured, with the result that a reduction in filmthickness was only about 6% and an increase in dielectric constant,which was measured to be about 2.6, was only 0.1. This has proved theexcellent heat resistance of the fluorinated amorphous carbon filmaccording to the second embodiment.

Although the second embodiment has used 1,1,1,3,3-pentafluoropropene asthe fluorinated carbon compound having a double bond of carbon atoms ina molecule thereof and containing a hydrogen atom, it is also possibleto use 1H,1H,2H-perfluorohexen, 1H,1H,2H-perfluoro-1-octene,trifluoroethylene, or 3,3,3-trifluoropropene instead.

Although the second embodiment has used the fluorinated carbon compoundhaving a double bond of carbon atoms in a molecule thereof andcontaining a hydrogen atom, it may also contain another component suchas N₂.

(Third Embodiment)

An interlayer insulating film according to a third embodiment is afluorinated amorphous carbon film formed by inducing plasmapolymerization of a material having, as a main component,hexafluoropropene which is a fluorinated carbon compound having a doublebond of carbon atoms in a molecule thereof and containing no hydrogenatom.

Since the third embodiment has been implemented by replacing thematerial used in the second embodiment, a description will be given onlyto the material.

When hexafluoropropene is introduced into the reaction chamber 11, it ispartially decomposed and changed into a plasma, while monomers, ions,and radicals are generated as decomposition products and polymerized toform the interlayer insulating film composed of the plasmapolymerization film on the semiconductor substrate 12.

Since hexafluoropropene according to the third embodiment contains nohydrogen atom, the resulting interlayer insulating film was afluorinated amorphous carbon film containing only carbon and fluorineatoms. The fluorinated amorphous carbon film had a dielectric constantof 2.3 immediately after deposition.

Since bonding in polymer composing the plasma polymerization film alsotends to be three-dimensional in the third embodiment, the film has ahigh glass transition temperature and excellent heat resistance.

To evaluate the heat resistance of the interlayer insulating filmaccording to the third embodiment, the semiconductor substrate 12 formedwith the fluorinated amorphous carbon film according to the thirdembodiment was held at a temperature of 400° C. in vacuum for 1 hour.The thickness and dielectric constant of the fluorinated amorphouscarbon film were then measured, with the result that a reduction in filmthickness was only about 5% and an increase in dielectric constant,which was measured to be about 2.5, was only 0.2. This has proved theexcellent heat resistance of the fluorinated amorphous carbon filmaccording to the third embodiment. Since the fluorinated amorphouscarbon film according to the third embodiment contains no hydrogen atomand is composed only of a fluorinated carbon, it has higher heatresistance and a lower dielectric constant than the fluorinatedamorphous carbon film according to the second embodiment.

Although the third embodiment has used the fluorinated carbon compoundhaving a double bond of carbon atoms in a molecule thereof andcontaining no hydrogen atom, it may also contain another component suchas N₂.

(Fourth Embodiment)

An interlayer insulating film according to a fourth embodiment is afluorinated amorphous carbon film formed by inducing plasmapolymerization of a material having, as a main component,hexafluoro-1,3-butadiene which is a fluorinated compound having twodouble bonds of carbon atoms in a molecule thereof and containing nohydrogen atom.

Since the fourth embodiment has been implemented by replacing thematerial used in the second embodiment, a description will be given onlyto the material. When hexafluoro-1,3-butadiene represented by thefollowing Chemical Formula 3 is introduced into the reaction chamber 11,it is partially decomposed to generate monomers, ions, and radicals asdecomposition products, which are polymerized to form the interlayerinsulating film composed of the plasma polymerization film on thesemiconductor substrate 12: ##STR3##

In the fourth embodiment, since hexafluoro-1,3-butadiene has two doublebonds of carbon atoms in a molecule thereof, the two double bondspartially decomposed in a plasma generate radicals each having fourunoccupied bonds, as shown by the following Chemical Formula 4, whichundergo polymerization: ##STR4## As a consequence, bonding in polymercomposing the plasma polymerization film positively becomesthree-dimensional, so that the crosslinking density and glass transitiontemperature of the resulting interlayer insulating film become higherthan in the second and third embodiments, resulting in improved heatresistance.

Although the fourth embodiment has used the fluorinated carbon compoundhaving two double bonds of carbon atoms in a molecule thereof andcontaining no hydrogen atom, it may also contain another component suchas N₂.

(Fifth Embodiment)

An interlayer insulating film according to a fifth embodiment is afluorinated amorphous carbon film formed by inducing plasmapolymerization of a material having, as a main component,3,3,3-trifluoropropyne which is a fluorinated carbon compound having atriple bond of carbon atoms in a molecule thereof and containing ahydrogen atom.

Since the fifth embodiment has been implemented by replacing thematerial used in the second embodiment, a description will be given onlyto the material.

When 3,3,3-trifluoropropyne (CF₃ C.tbd.CH) is introduced into thereaction chamber 11, it is partially decomposed to generate monomers,ions, and radicals as decomposition products, which are polymerized toform the interlayer insulating film composed of the plasmapolymerization film on the semiconductor substrate 12.

In the fifth embodiment, since 3,3,3-trifluoropropyne contains ahydrogen atom, the resulting interlayer insulating film is a fluorinatedamorphous carbon film containing a hydrogen atom as well as carbon andfluorine atoms. The fluorinated amorphous carbon film had a dielectricconstant of 2.5 immediately after deposition.

In the fifth embodiment, since 3,3,3-trifluoropropyne has a triple bondof carbon atoms in a molecule thereof, as shown by the followingChemical Formula 5, the triple bond partially decomposed in the plasmagenerate radicals each having four unoccupied bonds, as shown in thefollowing Chemical Formula 6, which undergo polymerization: ##STR5##

As a consequence, bonding in polymer composing the plasma polymerizationfilm positively becomes three-dimensional, so that the crosslinkingdensity and glass transition temperature of the resulting interlayerinsulating film become higher than in the second and third embodiments,resulting in improved heat resistance.

To evaluate the heat resistance of the interlayer insulating filmaccording to the fifth embodiment, the semiconductor substrate 12 formedwith the fluorinated amorphous carbon film according to the fifthembodiment was held at a temperature of 400° C. in vacuum for 1 hour.The thickness and dielectric constant of the fluorinated amorphouscarbon film were then measured, with the result that a reduction in filmthickness was only about 5% and an increase in dielectric constant,which was measured to be about 2.6, was only 0.1. This has proved theexcellent heat resistance of the fluorinated amorphous carbon filmaccording to the fifth embodiment.

Although the fifth embodiment has used 3,3,3-trifluoropropyne as thefluorinated carbon compound having a triple bond of carbon atoms in amolecule thereof and containing a hydrogen atom,perfluoro(t-butyl)acetylene (HC.tbd.CC(CF₃)₃) may be used instead.

Although the fifth embodiment has used the fluorinated carbon compoundhaving a triple bond of carbon atoms in a molecule thereof andcontaining a hydrogen atom, it may also contain another component suchas N₂.

(Sixth Embodiment)

An interlayer insulating film according to a sixth embodiment is afluorinated amorphous carbon film formed by inducing plasmapolymerization of a material having, as a main component,hexafluoro-2-butyne which is a fluorinated carbon compound having atriple bond of carbon atoms in a molecule thereof and containing nohydrogen atom.

Since the sixth embodiment has been implemented by replacing thematerial used in the second embodiment, a description will be given onlyto the material.

When hexafluoro-2-butyne (CF₃ C.tbd.CCF₃) is introduced into thereaction chamber 11, it is partially decomposed to generate monomers,ions, and radicals as decomposition products, which are polymerized toform the interlayer insulating film composed of the plasmapolymerization film on the semiconductor substrate 12.

In the sixth embodiment, since hexafluoro-2-butyne contains no hydrogenatom, the resulting interlayer insulating film is a fluorinatedamorphous carbon film containing only carbon and fluorine atoms. Thefluorinated amorphous carbon film had a dielectric constant of 2.3immediately after deposition.

In the sixth embodiment, since hexafluoro-2-butyne has a triple bond ofcarbon atoms in a molecule thereof, similarly to 3,3,3-trifluoropropynerepresented by the foregoing Chemical Formula 5, the triple bondpartially decomposed in a plasma generate radicals each having fourunoccupied bonds, similarly to the case of 3,3,3-trifluoropropyne, whichundergo polymerization. As a consequence, bonding in polymer composingthe plasma polymerization film positively becomes three-dimensional, sothat the crosslinking density and glass transition temperature of theresulting interlayer insulating film become higher than in the secondand third embodiments, resulting in improved heat resistance.

To evaluate the heat resistance of the interlayer insulating filmaccording to the sixth embodiment, the semiconductor substrate 12 formedwith the fluorinated amorphous carbon film according to the sixthembodiment was held at a temperature of 400° C. in vacuum for 1 hour.The thickness and dielectric constant of the fluorinated amorphouscarbon film were then measured, with the result that a reduction in filmthickness was only about 5% and an increase in dielectric constant,which was measured to be about 2.4, was only 0.1. This has proved theexcellent heat resistance of the fluorinated amorphous carbon filmaccording to the sixth embodiment.

Although the fifth embodiment has used the fluorinated carbon compoundhaving a triple bond of carbon atoms in a molecule thereof andcontaining no hydrogen atom, it may also contain another component suchas N₂.

(Seventh Embodiment)

An interlayer insulating film according to a seventh embodiment is afluorinated amorphous carbon film formed by inducing plasmapolymerization of a material having, as a main component,perfluorodecalin which is a fluorinated carbon compound having apolycyclic structure (condensed cyclic structure) in a molecule thereofand containing no hydrogen atom.

Since the seventh embodiment has been implemented by replacing thematerial used in the second embodiment, a description will be given onlyto the material.

When perfluorodecalin represented by the following Chemical Formula 7 isintroduced into the reaction chamber 11, it is partially decomposed togenerate monomers, ions, and radicals as decomposition products, whichare polymerized to form the interlayer insulating film made of theplasma polymerization film on the semiconductor substrate 12: ##STR6##

In the seventh embodiment, since perfluorodecalin contains no hydrogenatom, the resulting interlayer insulating film is a fluorinatedamorphous carbon film containing only carbon and fluorine atoms. Thefluorinated amorphous carbon film had a dielectric constant of 2.3immediately after deposition.

In the seventh embodiment, since perfluorodecalin has a polycyclicstructure (condensed structure) in a molecule thereof, as shown by theforegoing Chemical Formula 7, the polycyclic structure partiallydecomposed in a plasma generate radicals each having four unoccupiedbonds, as shown in the following Chemical Formula 8, which undergopolymerization: ##STR7##

As a consequence, bonding in polymer composing the plasma polymerizationfilm positively becomes three-dimensional, so that the crosslinkingdensity and glass transition temperature of the resulting interlayerinsulating film become higher than in the second and third embodiments,resulting in improved heat resistance.

To evaluate the heat resistance of the interlayer insulating filmaccording to the seventh embodiment, the semiconductor substrate 12formed with the fluorinated amorphous carbon film according to theseventh embodiment was held at a temperature of 400° C. in vacuum for 1hour. The thickness and dielectric constant of the fluorinated amorphouscarbon film were then measured, with the result that a reduction in filmthickness was only about 5% and an increase in dielectric constant,which was measured to be about 2.4, was only 0.1. This has proved theexcellent heat resistance of the fluorinated amorphous carbon filmaccording to the seventh embodiment.

Although the seventh embodiment has used perfluorodecalin as thefluorinated carbon compound having a polycyclic structure in a moleculethereof and containing no hydrogen atom, a fluorinated carbon compoundhaving a condensed cyclic structure such as perfluorofluorenerepresented by the following Chemical Formula 9,perfluoro-1-methyldecalin represented by the following Chemical Formula10, or perfluoro(tetradecahydrophenanthrene) represented by thefollowing Chemical Formula 11 may be used instead: ##STR8##Alternatively, it is also possible to use a fluorinated carbon compoundhaving a normal polycyclic structure such as perfluorobiphenylrepresented by the following Chemical Formula 12: ##STR9## (EighthEmbodiment)

An interlayer insulating film according to an eighth embodiment is asilicon oxide film containing a fluorinated carbon formed by inducingplasma polymerization of a material containing, as a main component, agas mixture of phenyltrimethoxysilane which is an organic siliconcompound represented by the following general formula:

    R.sup.1.sub.x Si(OR.sup.2).sub.4-x

(where R¹ is a phenyl group or a vinyl group; R² is an alkyl group; andx is an integer of 1 to 3) and a benzene derivative having a F--C bondwhich is a fluorinated carbon compound.

A description will be given to a method of forming the interlayerinsulating film according to the eighth embodiment.

First, the semiconductor substrate 12 is placed on the sample stage 13heated to, e.g., 400° C. and grounded by the change-over switch 14 andthen the reaction chamber 11 is evacuated by the vacuum pump 26.

Next, carrier gas composed of, e.g., argon is supplied at a flow rate of200 cc/min to the first container 24 containing thereinphenyltrimethoxysilane represented by the foregoing Chemical Formula 1,so that bubbled phenyltrimethoxysilane is introduced into the reactionchamber 11. Meanwhile, carrier gas composed of, e.g., argon is suppliedat a flow rate of 200 cc/min to the second container 25 containingtherein difluorobenzene which is a benzene derivative having a F--C bondrepresented by the following Chemical Formula 13 so that bubbleddifluorobenzene is introduced into the reaction chamber 11: ##STR10##

Next, the pressure inside the reaction chamber 11 is set to about 1.0Torr and RF power of 600 W at a frequency of 13.56 MHz is applied fromthe second RF power source 17 to the shower head 16 serving as the upperelectrode. During the process, phenyltrimethoxysilane gas anddifluorobenzene are partially decomposed to generate monomers, ions, andradicals as decomposition products, which are polymerized to form theinterlayer insulating film composed of the plasma polymerization film onthe semiconductor substrate 12. The structure of the plasmapolymerization film is diagrammatically shown by the following ChemicalFormula 14: ##STR11##

Since the interlayer insulating film according to the eighth embodimentis formed by plasma CVD, it is unnecessary to repeatedly perform thesteps of applying the organic SOG agent and thermally curing the appliedSOG agent several times, resulting in improved film formability andlower cost.

The dielectric constant of the interlayer insulating film according tothe eighth embodiment was as low as about 2.5. After the interlayerinsulating film was allowed to stand at room temperature for about 2weeks, the dielectric constant thereof was measured again to be about2.7, which indicates stable film quality scarcely varying with time.Thus, according to the eighth embodiment, there can be formed theinterlayer insulating film with improved film formability and a reduceddielectric constant.

The density of leakage currents was also measured to be about 4.5×10⁻⁸A/cm² at 5 MV/cm, which was satisfactory.

Although the pressure inside the reaction chamber 11 has been set toabout 1.0 Torr, it is not limited thereto but may be set at any valuewithin the range of 100 mTorr to 20 Torr. More preferably, the pressureinside the reaction chamber 11 is within the range of 0.5 to 5.0 Torr.

The RF power applied to the shower head 16 as the upper electrode mayhave any value within the range of 100 to 1000 W. More preferably, theRF power has a value within the range of 250 to 500 W.

Although the semiconductor substrate 12 may be heated to any temperaturewithin the range of 25 to 500° C., similarly to the first embodiment, itis preferably heated to a temperature within the range of 200 to 400° C.

As compounds represented by the foregoing general formula: R¹ _(x)Si(OR²)_(4-x) where R¹ is a phenyl group, there can be listeddiphenyldimethoxysilane in addition to phenyltrimethoxysilane. Ascompounds represented by the foregoing general formula: R¹ _(x)Si(OR²)_(4-x) where R¹ is a vinyl group, there can be listedvinyltrimethoxysilane and divinyldimethoxysilane.

As the benzene derivative having a F--C bond which is a fluorinatedcarbon compound, benzene fluoride such as fluorobenzene orhexafluorobenzene may be used instead of difluorobenzene.

(Ninth Embodiment)

An interlayer insulating film according to a ninth embodiment is asilicon oxide film containing a fluorinated carbon formed by inducingplasma polymerization of a material containing, as a main component, agas mixture of phenyltrimethoxysilane which is an organic siliconcompound represented by the following general formula:

    R.sup.1.sub.x Si(OR.sup.2).sub.4-x

(where R¹ is a phenyl group or a vinyl group; R² is an alkyl group; andx is an integer of 1 to 3) and C₂ F₆ which is a fluorinated carboncompound.

A description will be given to a method of forming the interlayerinsulating film according to the ninth embodiment.

First, the semiconductor substrate 12 is placed on the sample stage 13heated to, e.g., 400° C. and grounded by the change-over switch 14 andthen the reaction chamber 11 is evacuated by the vacuum pump 26.

Next, carrier gas composed of, e.g., argon is supplied at a flow rate of200 cc/min to the first container 24 containing thereinphenyltrimethoxysilane so that bubbled phenyltrimethoxysilane isintroduced into the reaction chamber 11, while C₂ F₆ gas is introducedinto the reaction chamber 11 through the third gas supply line 23.

Next, the pressure inside the reaction chamber 11 is set to about 1.0Torr and RF power of 700 W at a frequency of 13.56 MHz is applied fromthe second RF power source 17 to the shower head 16 serving as the upperelectrode. During the process, phenyltrimethoxysilane gas and C₂ F₆ arepartially decomposed to generate monomers, ions, and radicals asdecomposition products, which are polymerized to form the interlayerinsulating film composed of the plasma polymerization film on thesemiconductor substrate 12. The structure of the plasma polymerizationfilm is diagrammatically shown by the following Chemical Formula 15:##STR12##

Since the interlayer insulating film according to the ninth embodimentis formed by plasma CVD, it is unnecessary to repeatedly perform thesteps of applying the organic SOG agent and thermally curing the appliedSOG agent several times, resulting in improved film formability andlower cost.

The dielectric constant of the interlayer insulating film according tothe ninth embodiment was as low as about 2.9. After the interlayerinsulating film was allowed to stand at room temperature for about 2weeks, the dielectric constant thereof was measured again to be about3.0, which indicates stable film quality scarcely varying with time.Thus, according to the ninth embodiment, there can be formed theinterlayer insulating film with improved film formability and a reduceddielectric constant.

The density of leakage currents was also measured to be about 5.5×10⁻⁸A/cm² at 5 MV/cm, which was satisfactory.

Although the pressure inside the reaction chamber 11 has been set toabout 1.0 Torr, it is not limited thereto but may be set at any valuewithin the range of 100 mTorr to 20 Torr. More preferably, the pressureinside the reaction chamber 11 is within the range of 0.5 to 5.0 Torr.

The RF power applied to the shower head 16 as the upper electrode mayhave any value within the range of 100 to 2000 W. More preferably, theRF power has a value within the range of 300 to 750 W.

Although the semiconductor substrate 12 may be heated to any temperaturewithin the range of 25 to 500° C., it is preferably heated to atemperature within the range of 200 to 400° C.

As compounds represented by the foregoing general formula: R¹ _(x)Si(OR²)_(4-x) where R¹ is a phenyl group, there can be listeddiphenyldimethoxysilane in addition to phenyltrimethoxysilane. Ascompounds represented by the foregoing general formula: R¹ _(x)Si(OR²)_(4-x) where R¹ is a vinyl group, there can be listedvinyltrimethoxysilane and divinyldimethoxysilane.

As the fluorinated carbon compound, CF₄, C₄ F₈, or the like may be usedinstead of C₂ F₆.

Although the ninth embodiment has formed the interlayer insulating filmcomposed of the plasma polymerization film by causing the materialhaving, as a main component, an organic silicon compound represented bythe general formula R¹ _(x) Si(OR²)_(4-x) to undergo plasmapolymerization, the interlayer insulating film may also be formed bycausing the material having, as a main component, an organic siliconcompound represented by the following general formula:

    R.sup.1.sub.x SiH.sub.4-x

(where R¹ is a phenyl group or a vinyl group; and x is an integer of 1to 3) to undergo plasma polymerization or by causing the materialhaving, as a main component, an organic silicon compound represented bythe foregoing general formula:

    R.sup.1.sub.x Si(OR.sup.2).sub.4-x

or by the foregoing general formula:

    R.sup.1.sub.x SiH.sub.4-x

to react with an oxidizing agent made of, e.g., O₂ or H₂ O. In thiscase, O₂ gas or H₂ O gas as well as C₂ F₆ gas is introduced into thereaction chamber 11 through the third gas supply line 23.

As compounds represented by the foregoing general formula: R¹ _(x)SiH_(4-x) where R¹ is a phenyl group, there may be listed phenylsilaneand diphenylsilane. As compounds represented by the foregoing generalformula: R¹ _(x) SiH_(4-x) where R¹ is a vinyl group, there may belisted vinylsilane or divinylsilane.

(Tenth Embodiment)

An interlayer insulating film according to a tenth embodiment is asilicon oxide film containing a fluorinated carbon formed by inducingplasma polymerization of a material containing, as a main component, agas mixture of phenyltrimethoxysilane which is an organic siliconcompound represented by the following general formula:

    R.sup.1.sub.x Si(OR.sup.2).sub.4-x

(where R¹ is a phenyl group or a vinyl group; R² is an alkyl group; andx is an integer of 1 to 3) and perfluorodecalin which is the fluorinatedcarbon compound represented by the foregoing Chemical Formula 7.

A description will be given to a method of forming the interlayerinsulating film according to the tenth embodiment.

First, the semiconductor substrate 12 is placed on the sample stage 13heated to, e.g., 400° C. and grounded by the change-over switch 14 andthen the reaction chamber 11 is evacuated by the vacuum pump 26.

Next, carrier gas composed of, e.g., argon is supplied at a flow rate of280 cc/min to the first container 24 containing thereinphenyltrimethoxysilane so that bubbled phenyltrimethoxysilane isintroduced into the reaction chamber 11. Meanwhile, carrier gas composedof, e.g., argon is supplied at a flow rate of 42 cc/min to the secondcontainer 25 containing therein perfluorodecalin so that bubbledperfluorodecalin is introduced into the reaction chamber 11.

Next, the pressure inside the reaction chamber 11 is set to about 2.0Torr and RF power of 500 W at a frequency of 13.56 MHz is applied fromthe second RF power source 17 to the shower head 16 serving as the upperelectrode. During the process, phenyltrimethoxysilane gas andperfluorodecalin are partially decomposed to generate monomers, ions,and radicals as decomposition products, which are polymerized to formthe interlayer insulating film made of the plasma polymerization film onthe semiconductor substrate 12.

Since the interlayer insulating film according to the tenth embodimentis formed by plasma CVD, it is unnecessary to repeatedly perform thesteps of applying the organic SOG agent and thermally curing the appliedSOG agent several times, resulting in improved film formability andlower cost.

The dielectric constant of the interlayer insulating film according tothe tenth embodiment was as low as about 2.6. After the interlayerinsulating film was allowed to stand at room temperature for about 2weeks, the dielectric constant thereof was measured again to be about2.7, which indicates stable film quality scarcely varying with time.Thus, according to the tenth embodiment, there can be formed theinterlayer insulating film with improved film formability and a reduceddielectric constant.

Moreover, the interlayer insulating film had a glass transitiontemperature of 430° C. or more, which indicates excellent heatresistance.

Although the pressure inside the reaction chamber 11 has been set toabout 1.0 Torr, it is not limited thereto but may be set at any valuewithin the range of 100 mTorr to 20 Torr. More preferably, the pressureinside the reaction chamber 11 is within the range of 0.5 to 5.0 Torr.

The RF power applied to the shower head 16 as the upper electrode mayhave any value within the range of 100 to 1000 W. More preferably, theRF power has a value within the range of 250 to 500 W.

Although the semiconductor substrate 12 may be heated to any temperaturewithin the range of 25 to 500° C., similarly to the first embodiment, itis preferably heated to a temperature within the range of 200 to 400° C.

As compounds represented by the foregoing general formula: R¹ _(x)Si(OR²)_(4-x) where R¹ is a phenyl group, there may be listeddiphenyldimethoxysilane in addition to phenyltrimethoxysilane. Ascompounds represented by the foregoing general formula: R¹ _(x)Si(OR²)_(4-x) where R¹ is a vinyl group, there may be listedvinyltrimethoxysilane and divinyldimethoxysilane.

The fluorinated carbon compound is not limited to perfluorodecalin butthose shown in the second to seventh embodiments may be used properly.

(Eleventh Embodiment)

An interlayer insulating film according to an eleventh embodiment is asilicon oxide film containing a fluorinated carbon formed by inducingplasma polymerization of a material containing, as a main component, agas mixture of hexamethyldisiloxane which is a siloxane derivative andperfluorodecalin which is the fluorinated carbon compound represented bythe foregoing Chemical Formula 7.

A description will be given to a method of forming the interlayerinsulating film according to the eleventh embodiment.

First, the semiconductor substrate 12 is placed on the sample stage 13heated to, e.g., 400° C. and grounded by the change-over switch 14 andthen the reaction chamber 11 is evacuated by the vacuum pump 26.

Next, carrier gas composed of, e.g., argon is supplied at a flow rate of28 cc/min to the first container 24 containing thereinhexamethyldisiloxane so that bubbled hexamethyldisiloxane is introducedinto the reaction chamber 11. Meanwhile, carrier gas composed of, e.g.,argon is supplied at a flow rate of 280 cc/min to the second container25 containing therein perfluorodecalin so that bubbled perfluorodecalinis introduced into the reaction chamber 11.

Next, the pressure inside the reaction chamber 11 is set to about 0.8Torr and RF power of 250 W at a frequency of 13.56 MHz is applied fromthe second RF power source 17 to the shower head 16 serving as the upperelectrode. During the process, hexamethyldisiloxane and perfluorodecalinare partially decomposed to generate monomers, ions, and radicals asdecomposition products, which are polymerized to form the interlayerinsulating film composed of the plasma polymerization film on thesemiconductor substrate 12.

Since the interlayer insulating film according to the eleventhembodiment is formed by plasma CVD, it is unnecessary to repeatedlyperform the steps of applying the organic SOG agent and thermally curingthe applied SOG agent several times, resulting in improved filmformability and lower cost.

The dielectric constant of the interlayer insulating film according tothe eleventh embodiment was as low as about 2.75. After the interlayerinsulating film was allowed to stand at room temperature for about 2weeks, the dielectric constant thereof was measured again to be about2.8, which indicates stable film quality scarcely varying with time.Thus, according to the eleventh embodiment, there can be formed theinterlayer insulating film with improved film formability and a reduceddielectric constant.

Moreover, the interlayer insulating film had a glass transitiontemperature of 430° C. or more, which indicates excellent heatresistance.

Although the pressure inside the reaction chamber 11 has been set toabout 0.8 Torr, it is not limited thereto but may be set at any valuewithin the range of 100 mTorr to 20 Torr. More preferably, the pressureinside the reaction chamber 11 is within the range of 0.5 to 5.0 Torr.

The RF power applied to the shower head 16 as the upper electrode mayhave any value within the range of 100 to 1000 W. More preferably, theRF power has a value within the range of 250 to 500 W.

Although the semiconductor substrate 12 may be heated to any temperaturewithin the range of 25 to 500° C., similarly to the first embodiment, itis preferably heated to a temperature within the range of 200 to 400° C.

As the siloxane derivative, 1,1,3,3-tetramethyldisiloxane (H(CH₃)₂Si--O--Si(CH₃)₂ H, 1,3,5,7-tetramethylcyclotetrasiloxane represented bythe following Chemical Formula 16, or the like may be used instead ofhexamethyldisloxane: ##STR13##

The fluorinated carbon compound is not limited to perfluorodecalin butthose shown in the second to seventh embodiments may be used properly.

Although the eleventh embodiment has formed the interlayer insulatingfilm composed of the plasma polymerization film by causing the materialhaving the siloxane derivative as the main component to undergo plasmapolymerization, the interlayer insulating film may also be formed bycausing the material having the siloxane derivative as the maincomponent to react with an oxidizing agent made of, e.g., O₂ or H₂ O. Inthis case, O₂ gas, H₂ O gas, or the like is introduced into the reactionchamber 11 through the third gas supply line 23.

Although the argon gas has been used as the carrier gas in each of thefirst to eleventh embodiments, hydrogen, nitrogen, or helium may also beused properly instead of the argon gas.

Although the sample stage 13 as the lower electrode has been grounded ineach of the first to eleventh embodiments, if the RF power is appliedfrom the first RF power source 15 to the sample stage 13 by using thechange-over switch 14, a plasma composed of a reactive gas generated inthe reaction chamber 11 can be supplied efficiently to the sample stage13, so that the speed at which the interlayer insulating film is formedis increased about two- to five-fold.

We claim:
 1. A method of forming an interlayer insulating film, whereina material containing, as a main component, an organic silicon compoundrepresented by the following general formula:

    R.sup.1.sub.x Si(OR.sup.2).sub.4-x

(where R¹ is a phenyl group or a vinyl group; R² is an alkyl group; andx is an integer of 1 to 3) is caused to undergo plasma polymerization orreact with an oxidizing agent to form an interlayer insulating filmwhich is composed of a silicon oxide film containing an organiccomponent and has a structure in which constituents are not regularlyarranged.
 2. A method of forming an interlayer insulating film accordingto claim 1, wherein said organic silicon compound isphenyltrimethoxysilane or diphenyldimethoxysilane.
 3. A method offorming an interlayer insulating film according to claim 1, wherein saidorganic silicon compound is vinyltrimethoxysilane ordivinyldimethoxysilane.
 4. A method of forming an interlayer insulatingfilm, wherein a material containing, as a main component, an organicsilicon compound represented by the following general formula:

    R.sup.1.sub.x SiH.sub.4-x

(where R¹ is a phenyl group or a vinyl group; and x is an integer of 1to 3) is caused to undergo plasma polymerization or react with anoxidizing agent to form an interlayer insulating film which is composedof a silicon oxide film containing an organic component and has astructure in which constituents are not regularly arranged.
 5. A methodof forming an interlayer insulating film according to claim 4, whereinsaid organic silicon compound is phenylsilane or diphenylsilane.
 6. Amethod of forming an interlayer insulating film according to claim 4,wherein said organic silicon compound is vinylsilane or divinylsilane.7. A method of forming an interlayer insulating film, wherein a materialcontaining, as a main component, an organic silicon compound representedby the following general formula:

    R.sup.1.sub.x Si(OR.sup.2).sub.4-x

(where R¹ is a phenyl group or a vinyl group; R² is an alkyl group; andx is an integer of 1 to 3) is caused to undergo plasma polymerization bymeans of plasma chemical vapor deposition to form an interlayerinsulating film which is composed of a silicon oxide film containing anorganic component and has a structure in which constituents are notregularly arranged.
 8. A method of forming an interlayer insulatingfilm, wherein a material containing, as a main component, an organicsilicon compound represented by the following general formula:

    R.sup.1.sub.x SiH.sub.4-x

(where R¹ is a phenyl group or a vinyl group; and x is an integer of 1to 3) is caused to undergo plasma polymerization by means of plasmachemical vapor deposition to form an interlayer insulating film which iscomposed of a silicon oxide film containing an organic component and hasa structure in which constituents are not regularly arranged.